1. Field of the Invention
The present invention relates to a novel method and apparatus for monitoring and/or controlling tephritid fruit flies using chemical and visual stimuli.
2. Description of the Art
Control of frugivorous pest flies is of considerable economic importance for fruit and vegetable production and export. Quarantine and regulatory agents expend substantial efforts to detect newly introduced species of economically important fruit flies. The Mediterranean fruit fly, Ceratitis capitata is a major frugivorous pest due to its wide distribution and large host range (Enkerlin et al., World Crop Pests, Vol. 3A; Fruit Flies, Their Biology, Natural Enemies and Control, Elsevier Science Publishers, 1989). Because of its threat and the potential for its introduction into the United States, much emphasis has been placed on detection and eradication of C. capitata. The development of improved lures is needed to monitor and suppress populations of this and other pest fruit flies, and to prevent establishment of populations in areas that are currently without these pests.
Methods developed for monitoring, controlling, and eradicating frugivorous fruit flies (Tephritidae) have relied extensively on the use of chemical attractants. Methyl eugenol plus dibrom; cuelure plus dibrom; ammonium salts; and a mixture of 1,7-dioxaspiro 5.5! undecane with .alpha.-pinene or n-nonanal; and spiroacetal are used as lures for species of Dacus. A composition of hexyl acetate, (E)-2-hexen-1yl acetate, butyl 2-methylbutanoate, propyl hexanoate, hexyl propanoate, butyl hexanoate, and hexyl butanoate is used as a lure for species of Rhagoletis. Trimedlure (Beroza et al., J. Agric. Food Chem. 9:361-365,1960) is used to attract male Mediterranean fruit flies. Although trimedlure is effective in attracting male Mediterranean fruit flies, it is either only weakly active in attracting or is completely ineffective in attracting female Mediterranean fruit flies (Nakagawa et al., Journal of Economic Entomology 63: 227-229, 1970). Conventional lures currently used to survey and detect frugivorous pests are protein baits such as fermenting yeast hydrolysate (Greany et al., Ent. exp & Appl. 21:63-70, 1977) and protein hydrosylate (McPhail, J. Econ. Entomol. 32:758-761, 1939). The problem with protein lures is that they capture large numbers of nontarget insects. Furthermore, the only lures that are available for attracting both female and male fruit flies are protein baits.
Adult fruit flies require sugar to survive (Christenson & Foote, Annual Review of Entomology 5:171-192, 1960), and honeydew secreted by homopterous insects is recognized as an important food source for adult tephritids (Christenson et al., Annual Review of Entomology 5:171-192, 1960). Female fruit flies also require protein to ensure fecundity, and this protein requirement is the primary basis for traps for detection of female fruit flies. McPhail traps, bell-shaped glass traps with a water reservoir (Newell, Journal of Economic Entomology 29:116-120, 1936), baited with protein bait are currently used for monitoring fruit flies throughout fruit growing areas of the world. McPhail traps are cumbersome and use of these traps have numerous disadvantages. Servicing the trap requires that water and bait be added in a somewhat maladroit manner in which the trap is turned upside down, bait added and then the trap returned to an upright position. This process often results in bait spillage, and the spilled bait becomes a food source for flies outside the trap. Removal of insects trapped also requires considerable effort as the contents of the trap have to be filtered through a mesh screen to separate the insects from the bait solution. Protein bait solutions capture a large number of non-targeted insects and considerable time is required to sort the pest fruit flies from the non-targeted insects. The fruit flies recovered from these traps are often severely decomposed with parts missing. This increases the difficulty of differentiating marked sterile flies from unmarked fertile flies when these traps are used in conjunction with sterile insect release programs. Other factors that contribute to the difficulty in the deployment of McPhail traps include the size and weight of the trap and the fragile nature of glass.
Hundreds of compounds are known to be released from protein baits (Morton & Bateman, Aust. J. Agric. Res. 32:905-916, 1981). Examples of some volatile components of commercial hydrolyzed protein insect baits are phenylacetaldehyde, acetic acid, furfuryl alcohol, 2-acetylfuran, benzaldehyde, methanol, 2-acetylpyirole, furfural, 5-methyl-2-phenyl-2-hexenal, 5-methyl-2-(methylthio)methyl!-2-hexenal and ammonia. Ammonia (Bateman & Morton, Aust. J. Agric. Res. 32:883-903, 1981; Mazor et al., Entomol. Exp. Appl. 43:25-29, 1987), acetic acid (Keiser et al., Lloydia 38: 141-152, 1976), and various other volatiles (Buttery et al., J. Agric. Food Chem. 31: 689-692, 1983) have been investigated as attractants for fruit flies. These reports, however, do not provide information regarding released amounts or ratios of the compounds tested or the effectiveness of these chemicals as compared to McPhail traps.
A number of tephritid fruit flies are known to be attracted to certain colors and shapes as visual mimics of foliage or fruit. It has been reported that tephritid species such as the Caribbean fruit fly, Anastrepha suspensa (Loew); the apple maggot fly, Rhagoletis pomonella (Walsh); the European cherry fruit fly, R. cerasi (L.); the Mediterranean fruit fly, and the olive fruit fly are attracted to yellow rectangular panels, i.e. two-dimensional visual cues mimicking foliage (Greany et al., Entomol. Exp. Appl. 21: 63-70, 1977; Prokopy, Environmental Entomology 1: 720-726, 1972; Prokopy & Boller, Journal of Economic Entomology 64: 1444-1447, 1971; Prokopy & Economopoulos, Z Ang. Entomol. 80: 434-437, 1976). Painted spheres, i.e., three-dimensional visual cues mimicking host fruit, have been reported to be attractive to the apple maggot fly (dark red spheres); the walnut husk fly, R. completa Cresson, (green spheres); and the Mediterranean fruit fly (black or yellow spheres) (Prokopy, Canadian Entomologist 109: 593-596, 1977; Riedl & Hislop, Environmental Entomology 14: 810-814, 1985; Nakagawa et al., Entomol. Exp. Appl. 24: 193-198, 1978). Currently all traps using visual cues either singularly or in combination with chemical attractants rely on the use of sticky materials to retain the captured insects. These materials are difficult to use and the traps need constant maintenance to remove numerous non-targeted flies captured as well as need to replenish the sticky material.
Some species of fruit flies have been trapped with a combination of visual stimuli of fruit or foliage mimics and non-pheromonal chemical lures. Reissig et al., Environmental Entomology 11:1294-1298, 1982, disclose trapping apple maggot flies using red spheres baited with synthetic apple volatiles. Riedl & Hislop, supra, reported that the addition of ammonium carbonate as a food-based stimulus enhanced the response of walnut husk flies to yellow rectangles and green spheres but there was a loss of selectivity for the walnut husk fly. Nakagawa et al., supra, reported that the addition of the chemical lure trimedlure to yellow rectangles or black spheres enhanced attraction for male Mediterranean fruit flies. Combinations of pheromone-based lures with visual mimics have been reported. Successful field testing of sex pheromone baited traps for males of the olive fruit fly, Dacas oleae (Gmelin) has been demonstrated using the female-produced pheromone (Jones et al., Bulletin of Entomological Research 73:97-106, 1983; Mazomenos & Haniotakis, Journal of Chemical Ecology 11:397-405, 1985). Trapping of female fruit flies based on male-produced pheromone in combination with a sphere as a visual cue has been reported for the Mediterranean fruit fly (Heath et al., Journal of Chemical Ecology 17:1925-1940) and the papaya fruit fly, Toxotrypana curvicauda Gerstaecker, (Landolt et al., Environmental Entomology 21:1154-1159, 1992). Attraction of female fruit flies to male pheromone occurs only when the female fly is physiologically ready to mate. Thus, female fruit flies may be attracted to male-produced sex pheromone for only brief periods of their adult life span, and none are currently in use for standard trapping procedures.
To date, there is no food-based attractant system for both male and female fruit flies that does not use either aqueous bait solution in glass traps or synthetic chemicals in traps with sticky material to capture these fruit flies. Thus more convenient methods are needed to provide a "dry" insect trap for monitoring the Mediterranean fruit fly.